By using density functional theory (DFT), we investigate the structure, stability, electronic properties and reactivity of nanometer size Pt13 cluster deposited on relevant ?-alumina surfaces exhibiting various hydroxylation and chlorination states.1 This size of the cluster is at the lower limit of the catalytic objects that can be created and characterized experimentally and presents a strong interest for reforming reactions. The behavior of larger particles is inferred from extended surface models.The particle is submitted to a pressure of hydrogen or CO, the equilibrium coverage and shape of the cluster is explored from ab initio thermodynamics. Pt13 particle on alumina show a much stronger adsorption of hydrogen compared to extended surface hence leading to high H coverage (up to 3 H/Pt) and to the formation of a surface hydride.2 Hydrogen uptake is associated with a change of the shape of the cluster and a weakening of the cluster/support interaction. The thermodynamic stability of various CxHy intermediates from reaction of ethane is explored for various pressure ratio J = P(H2)/P(C2H6), corresponding to different H coverage on the particle. A strong impact of operating conditions is shown on the free energy profile and on the relative stabilities of C1 and C2 intermediates.3 DFT calculations hence allow the understanding of the stability, structure and chemical reactivity of small Pt particles deposited on alumina as a function of reaction conditions. References 1.      Mager-Maury,C.; Bonnard, G.; Chizallet, C.; Sautet, P. and Raybaud, P. ACS Catalysis 2012 , 2, 1346.2.      Mager-Maury, C.;Bonnard, G.; Chizallet, C.; Sautet, P. and Raybaud, P. ChemCatChem 2011 , 3, 2003.      Raybaud, P.; Chizallet, C.; Mager-Maury, C.; Digne, M.; Toulhoat, H.; Sautet, P. J. Catal. 2013  (in press).

Structure and catalytic reactivity of nanometer size Pt clusters: Insights from DFT

247th National Meeting (2014)

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